Mobile communication networks rely on mobile base transceiver stations (BTSs) to facilitate wireless communication between user equipment and a network. BTSs receive and transmit signals between user equipment and the network, and one component of a BTS is its power amplifier (PA). The PA is configured to amplify weak signals without adding distortion. The PA is usually power hungry, typically consuming 30% (or more) of total power. Furthermore, the PA is expensive, usually making up 30% (or more) of the total cost of the BTS.
One characteristic of a power amplifier is that when the input power is relatively small, the output power is also relatively small. In this operating zone, the PA behaves linearly, but the PA is not very efficient. When the input power is relatively high, the output power is also high. In this operating zone, the PA is very efficient, but the PA loses its linearity. Such non-linearity generates undesirable effects in the signal itself as well as in adjacent channels. The problem is particularly significant when PAs are used in mobile BTSs because of mobile communication standards often use non-constant envelop modulation techniques. Thus, the PA in the BTSs ought to achieve high efficiency and linearity over a large amplitude range to maintain high adjacent channel leakage ratio (ACLR) and low error vector magnitude (EVM). While solutions have been used to correct the non-linearity effect, the issue resulting from the non-linearity remains hard to correct because, among other things, the effect depends on the previous signal in the time domain (a memory effect).